Differential functions of C- and N-terminal hepatitis B x protein in liver cells treated with doxorubicin in normoxic or hypoxic condition.

Abstract

Hepatitis viral B x protein (HBx), a hepatocarcinogen, is frequently mutated. Hypoxia influences the growth of HCC and also the sensitivity of tumor cells to treatments. We aimed to test the role of HBx and acute hypoxia in the efficacy of chemotherapy. In this study, we established 4 Chang liver cell lines with the full-length HBx (HBx), the first 50 amino acids of N-terminal HBx (HBx/50), the last 104 amino acids of C-terminal HBx (HBx/51) and empty vector (CL), respectively. MTT and TNUEL assays were used to assess cell viability and apoptosis respectively. Western blot was used to determine the expression of relevant proteins. Results showed that among 4 cell lines, doxorubicin was most effective in decreasing the viability and enhancing apoptosis in HBx/51 cells, while HBx/50 cells were most resistant to the treatment. Cells in hypoxia were more susceptible to doxorubicin than cells in normoxia. Hypoxia facilitated the Bid cleavage especially in HBx/51 cells via phosphorylating p38 MAPK. p38 MAPK inhibitor significantly reduced the tBid level and increased cell viability. In conclusion, N-terminal HBx and C-terminal HBx function differentially in their ability to regulate cell growth, with the former being promotive but the latter being inhibitory. The acute hypoxia may overcome the HBx-induced resistance and facilitate the chemotherapy.

• Authors: Davor Kin-Fan Chau, George Gong Chen, Haitao Zhang, Billy Cheuk Sing Leung, Sukying Chun, Paul Bo-San Lai
• Journal: PloS one (PLoS One) Vol. 7 Issue 11 Pg. e50118 ( 2012) ISSN: 1932-6203 [Electronic] United States
• PMID: 23209654 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• HIF1A protein, human
• Hypoxia-Inducible Factor 1, alpha Subunit
• Trans-Activators
• Viral Regulatory and Accessory Proteins
• hepatitis B virus X protein
• Doxorubicin
• p38 Mitogen-Activated Protein Kinases

Topics

• Apoptosis
• Cell Culture Techniques
• Cell Line, Tumor
• Cell Survival
• Cells, Cultured
• Doxorubicin (pharmacology)
• Gene Expression Regulation, Neoplastic
• Gene Expression Regulation, Viral
• Humans
• Hypoxia
• Hypoxia-Inducible Factor 1, alpha Subunit (metabolism)
• In Situ Nick-End Labeling (methods)
• Liver (metabolism)
• Liver Neoplasms (virology)
• Mutation
• Protein Structure, Tertiary
• Trans-Activators (chemistry, physiology)
• Viral Regulatory and Accessory Proteins
• p38 Mitogen-Activated Protein Kinases (metabolism)